St. Marie: Demographics & People
About 306 people live in St. Marie, in 92 households. Population shrank 4.1% from 319 (2022) to 306 (2024). Median age 37.9 years. (13.0y younger than Golden Valley County; 2.9y younger than Montana). Children under 18 are 4% of the population. Population is 56% White (non-Hispanic). The community is relatively homogeneous (Simpson index 0.00). 60% of households are family-led. County is losing 118 residents per year (2022-2023). County health: 34% adult obesity, 20% smoke.
- 3.3 people per household.
- 40% non-family households (singles, roommates).
Population & Trend
Population shrank 4.1% from 319 (2022) to 306 (2024). Estimated 2026 population: ~293 (extrapolated at -2.0%/yr trend). Census Bureau Vintage estimate: 277.
| Census data vintage | 2024 |
|---|---|
| Population | 823 people |
| Annual growth rate · Population change | -4.1% |
| Annual growth rate · Population (2022) | 319 |
| Annual growth rate · Population (2024) | 306 |
| Annual growth rate · Trend category | declining |
| Population | 306 people |
| Population Estimate | 277 |
Sources: Census ACS 5-Year 2023, Table B01003 · Refreshed 2026-04-12
Age Distribution
Median age 37.9y is 1.0 years younger than the U.S. median (38.9y). Children under 18 make up 4% — below the U.S. share of ~22%.
| Age Summary · Median age | 37.9 years (vs Montana 40.8y) |
|---|---|
| Age Summary · Children Pct | 4.2% |
| Age Summary · Character | family-oriented |
| Population under 18 | 13 |
| Median age | 37.9 years (vs Montana 40.8y) |
Sources: Census ACS 5-Year 2023 · Refreshed 2026-04-12
Race, Ethnicity & Diversity
Of 306 residents, race / ethnicity breaks down by Census ACS counts (a person can identify with one or more groups). The Simpson diversity index is 0.00 (0 = single group, 1 = perfectly even distribution); this is read as relatively homogeneous.
| White residents | 178 |
|---|---|
| Diversity Index · Diversity label | relatively homogeneous |
| Diversity Index · Groups counted | 1 |
| Diversity Index · Largest group share | 100.0% |
| White (non-Hispanic) population | 55.9% |
Sources: Census ACS 5-Year 2023 · Refreshed 2026-04-12
Ancestry
Self-reported ancestry from Census ACS — what residents report as their ethnic origin, separate from race. Counts can exceed population because people can list multiple ancestries.
Top (2)
Citizenship & Origin
Where residents were born and their citizenship status (Census ACS).
| Residents born in this state | 64 |
|---|---|
| Residents born in another state | 242 |
| Share born in this state | 20.9% |
| Share born in another state | 79.1% |
| Native-born U.S. citizens | 79.1% |
| Total foreign-born residents | 11 |
Households & Family Composition
92 households. Averaging 2.7 people each — larger than the U.S. average of 2.5. 60% are family households — below the U.S. share of ~65%. Of 50 families, 20% are married couples with children.
| Children under 18 | 10 |
|---|---|
| Total families | 50 |
| Married couples with children | 10 |
| Average household size | 2.66 |
| Women who gave birth (past year) | 2.0% |
| Family households | 55 households |
| Households that are families | 59.8% |
| Total households | 92 households |
Sources: Census ACS 5-Year 2023 · Refreshed 2026-04-12
Residential Stability & Migration
How long residents have lived here and where they came from. 2.6% moved within the county in the past year — the U.S. baseline is roughly 8–10%. The surrounding county is losing 118 residents per year on net (IRS migration data).
| Moved within the county (past year) | 2.6% |
|---|---|
| Migration · People moving in (annual) | 698 |
| Migration · People moving out (annual) | 816 |
| Migration · Net migration (in − out) | -118 |
| Migration · Year | 2022-2023 |
Sources: IRS SOI Migration 2021-2022 · Refreshed 2026-04-12
Disability
Census ACS measures self-reported functional limitations — vision, hearing, mobility, cognitive, self-care, or independent-living. The U.S. baseline disability rate is about 12–13%; rates trend higher with median age.
| Residents with a disability | 58 |
|---|---|
| Disability rate | 13.6% |
Other
| Congressional District · District | 2 |
|---|---|
| Congressional District · Formatted | MT-02 |
| Congressional District · Congress | 118th |
| Cdc Birth Rate · Fips | 30,037 |
| Cdc Birth Rate · State Fips | 30 |
| Cdc Birth Rate · County Fips | 37 |
| Cdc Birth Rate · County | Golden Valley |
| Cdc Birth Rate · Birth Rate | 7.4% |
| Cdc Birth Rate · Lower Ci | 1.00 |
| Cdc Birth Rate · Upper Ci | 26.30 |
| Cdc Mortality · Fips | 30,037 |
| Cdc Mortality · County | Golden Valley County |
| Cdc Mortality · Urban Rural | Small metro |
| Cdc Mortality · Total Deaths 2020 2023 | 34 |
| Cdc Vaccination · Fips | 30,037 |
| Cdc Vaccination · County | Golden Valley County |
| Cdc Vaccination · Dose1 Pop Pct | 54.7% |
| Cdc Vaccination · Series Complete Pct | 48.0% |
| Cdc Vaccination · Booster Pct | 44.9% |
| Cdc Vaccination · Population 2019 | 821 |
| Cdc Vaccination · Metro Status | Metro |
| Family Score · Score | 10 |
| Family Score · Schools | 20 |
| Family Score · Children Pct | 4.2% |
| Family Score · Rating | excellent |
| Town Summary · Key Facts | population 306, declining, family-oriented, working-class, mixed |
| Town Summary · Population | 306 people |
| Town Summary · County | Golden Valley County |
Sources: Census place-to-CD118 crosswalk (place_fips) · federal dataset cascade